Recently, in mobile devices such as smartphones, tablets, lap-top PCs (Personal Computers), or the like, an amount of heat that is generated per unit area is increasing due to improvements in performance and reduction of size of the mobile devices, including reduction in thicknesses of the mobile devices.
In the mobile devices described above, it is difficult to provide a built-in fan for air-cooling or a built-in pump for water-cooling, due to the limited size of the mobile devices. Hence, the mobile devices use for cooling a metal sheet having a high thermal conductivity.
However, as the amount of heat that is generated further increases, it becomes more difficult to sufficiently dissipate the heat using only the metal plate. Accordingly, a loop heat pipe has been developed. The loop heat pipe includes an evaporator for absorbing the heat of a heat generating component, a condenser for dissipating the heat, and pipes connecting the evaporator and the condenser in a loop. A working fluid is sealed within the pipes.
Examples of heat pipes are proposed in Japanese Laid-Open Patent Publication No. 11-287577, International Publication Pamphlet No. WO2015/087451, and Japanese Laid-Open Patent Publication No. 2016-95108, for example.
When accommodating the loop heat pipe in an electronic device, it may be required to adjust a height position of at least one of the evaporator and the condenser. In this case, the pipes connecting the evaporator and the condenser need to be bent.
However, the inside of each pipe is a small rectangular hollow space. For this reason, when the pipe is bent, compressive stress is generated at a pipe wall on an inner part relative to a bending direction, and the pipe wall on the inner part is pushed and moved toward the inside of the pipe. On the other hand, tensile stress is generated at a pipe wall on an outer part relative to the bending direction, and the pipe wall on the outer part is pulled and moved toward the inside of the pipe. As a result, the pipe may be blocked or closed, to prevent the loop heat pipe from functioning properly.